In rotary indexing systems it is desirable to be able to accommodate variable processing intervals. One way of accomplishing this result is to vary the frequency of the processing tool while holding the movement of the material web constant past the tool. Another way is to vary the movement of the material web while holding the frequency of the processing tool constant.
The instant invention provides an apparatus for driving the material webs at adjustable strokes. The size of the stroke determines the size of the processing interval. The invention uses a crank-rocker four-link linkage between a driving input shaft and the output shaft with a one-way clutch on the output shaft.
The instant invention utilized the following criteria defining the kinematics of crank-rocker four-link mechanisms. A planar four-link mechanism will have a crank and rocker if: (1) the crank is the shortest link, and (2) the sum of the links of the longest and shortest links is less than or equal to the sum of the lengths of the other two links. The angular indexing stroke is the magnitude of the smallest angle between the two limit positions of the rocker arm. The stroke may be changed by changing only the length of the input crank.